This invention is concerned with lubricants for wires with lacquer and enamel insulation.
Lacquered and enameled wires, i.e. wires with lacquer or enamel insulation, have a thin lacquer or enamel film, as blister- and pore-free as possible, whose thickness is established according to standard regulations. The lacquer film serves to insulate the turns of a coil of wire from one another. Lacquered and enameled wires for electrical machine construction, and also those for low-voltage engineering, are subjected to high stress during their fabrication or during winding on automatic winders or when being inserted into grooves of stators or rotors of electric machines.
To avoid damage to the wire insulation during fabrication and to permit satisfactory winding, the wires are coated with lubricants. Thereby the mechanical forces acting on the lacquer or enamel coating are reduced.
In electric machine construction it is customary, in order to enhance electrical and mechanical-thermal properties, to impregnate the windings by immersion or trickling methods with unsaturated polyester or epoxy resins, and then to bake them in a tempering or annealing process.
Lubricants known in the art, especially paraffin-based lubricants, greatly reduce the strength of the bond between lacquered or enameled wire and impregnating resin. The lubricants possess the undesirable property of forming a kind of separating layer between the impregnating resin and the lacquered or enameled wire. The strength reduction can be shown clearly in switching tests on electric motors, when comparing testpieces with lubricant-free windings with testpieces whose windings are provided with lubricants. An additional operation to remove the lubricants before the impregnation or immersion process, whereby the above-mentioned difficulties could be eliminated, is economically unacceptable on a large scale.